Over the past few years, several feeder breakers have tripped. In all but one case, the cause was traced to a branch circuit condition, but the branch circuit breaker did not trip.
After the first two incidents, a breaker coordination study was conducted and a few changes were made. Yet, the problem recurred. Management’s response was to:
- Consult each breaker manufacturer about the recommended lubricant for their breaker.
- Evaluate and improve breaker maintenance procedures.
- Assign and train people specifically for breaker maintenance.
- Dedicate test equipment and put it on a calibration program.
- Increase the breaker maintenance frequency.
Recently, someone suggested you’re a circuit breaker guru, and the plant engineer bought that. Where should you look to solve this?
The typical maintenance procedure does not capture first trip data. If your PMs do not already include capturing first trip data, consult with a qualified electrical testing firm about performing this work for you at least the first time through.
You’ll possibly find a high failure rate in this testing. A common cause is that the breakers are simply too old. You can lubricate and exercise them regularly, but you just can’t get past age with this equipment. Possibly they are (also) exposed to contaminants (e.g., dust) that gum up the lubricant. Thus, determine breaker age and assess the environment they are in. Consider outsourcing the breaker PMs.
